This invention relates generally as indicated to aircraft deicing equipment and, more particularly, to a pneumatic deicer wherein the surfaces defining inflation passages are appropriately coated to deter undesired moisture absorption.
An aircraft may be periodically exposed to conditions of precipitation and low temperatures which may cause the forming of ice on the leading edges of its wings and/or on other airfoils during flight. If the aircraft is to perform sufficiently in flight, it is important that this ice be removed. To this end, various types of aircraft deicers have been developed to address this issue. An aircraft deicer is designed to break up ice accumulations which undesirably tend to form on certain airfoils (such as the leading edges of the aircraft""s wings) when the aircraft is operating in severe climatic conditions.
Of particular interest to the present invention is pneumatic aircraft deicers. A pneumatic deicer typically comprises a deicing panel that is installed on the surface to be protected, such as the leading edge of an aircraft wing. One surface of the deicing panel is adhesively bonded to the wing and this surface is referred to as the xe2x80x9cbondsidexe2x80x9d surface. The other surface of the deicing panel is exposed to the atmosphere and this surface is referred to as the xe2x80x9cbreezesidexe2x80x9d surface. For sake of directional clarity, the terms xe2x80x9cbondsidexe2x80x9d and xe2x80x9cbreezesidexe2x80x9d may be used to refer to the location of respective surfaces of the deicer and its components relative to the wing. Specifically, a bondside surface would be the surface relatively closest to the wing and a breezeside surface would be the surface relatively most removed from the wing.
The panel of a pneumatic deicer also includes inner surfaces which define inflatable passages. An inflation fluid, such as air, is repeatedly alternately introduced and evacuated from the passages via tubes or other suitable connection means during operation of the deicer. The cyclic inflation and deflation of the passages causes a change in the bondside surface geometry and surface area thereby imposing shear stresses and fracture stresses upon the sheet of ice. The shear stresses displace the boundary layer of the sheet of ice from the deicer""s breezeside surface and the fracture stresses break the ice sheet into small pieces which may be swept away by the airstream that passes over the aircraft wing.
A pneumatic deicer will typically be constructed from a plurality of layers including two passage-defining layers which define the inflation passages. These passage-defining layers are commonly viewed as the carcass of the deicer and/or the deicer panel. One of the passage-defining layers is usually non-deformable and includes a breezeside surface which is a passage-defining surface. The other of the passage-defining layers is deformable and includes a bondside surface which is a passage-defining surface. When the passages are inflated, the passage-defining surfaces are in contact with the inflation fluid.
The carcass layers typically each comprise a fabric ply coated on one side with rubber or another similar coating. For example, the non-deformable layer may comprise a square-woven fabric while the deformable layer may comprise a knit fabric. The carcass is manufactured by sewing the coated fabric layers together with the uncoated fabric surfaces facing each other. Thus, the uncoated fabric surfaces will form the passage-defining surfaces of the deicer.
When the passages are deflated and/or are being deflated, the texture of the uncoated fabric surfaces prevents flow-precluding contact between these surfaces as the inflation fluid is being evacuated from the passages. In other words, the texture of the fabric prevents the entrapment of inflation fluid. Thus, the texture of the uncoated fabric has conventionally been viewed as allowing the air to pass more freely through the carcass during deflation thereby allowing the deicer to xe2x80x9cbreathe.xe2x80x9d
When the passages are inflated or are being inflated, the uncoated fabric surfaces are in contact with the inflation fluid (e.g., air) and the coating on the opposite fabric surfaces prevent the escape of inflation fluid from the passages. Accordingly, the adhesion between the coating and the fabric is a significant factor in deicer operability. For this reason, the fabric plies are often treated with an RFL (resorcinol-formaldehyde-latex) dip prior to application of the coating to promote adhesion between the fabric and its coating.
The inventors appreciated that moisture may be present in the inflation fluid whereby water is introduced into the inflation passages during operation of the deicer. The inventors additionally appreciated that moisture absorbed through the uncoated fabric surfaces of the carcass layers may cause a weakening, or even a failure, of the adhesive bond between the fabric and the rubber coating thereby reducing the useful life of the deicer. While an RFL dip may serve to promote adhesion between the fabric and its coating, the strength of adhesion may be reduced by the presence of liquid water, particularly at warmer temperatures.
The present invention provides a deicer for an aircraft wherein the passage-defining surfaces are coated with a water impervious coating to prevent the absorption of moisture through the fabric plies of the carcass layers.
More particularly, the present invention provides a deicer for breaking up and removing accumulated ice on an airfoil surface. The deicer comprises a bondside surface which is bonded to the airfoil surface, a breezeside surface on which the ice will accumulate, and passage-defining surfaces therebetween. The passage-defining surfaces define a plurality of expansible and contractible inflation passages and include a moisture-impervious coating. The deicer may comprise a deicer panel (which includes the bondside surface, the breezeside surface and the passage-defining surfaces) and means for introducing inflation fluid to and evacuating inflation fluid from the passages. Thus, when the deicer is bonded to an airfoil surface of an aircraft (such as the leading edge of a wing), the expansion and contraction of the inflation passages will break up and remove the accumulated ice.
The deicer panel may comprise a carcass which includes the passage-defining surfaces, such as a carcass formed from a first layer and a second layer which are joined together to form the inflation passages. The first layer may comprise a first fabric ply (such as RFL treated nylon square woven fabric) and the moisture-impervious coating (such as natural rubber) would be on the breezeside surface of the first fabric ply. The second layer may comprise a second fabric ply (such as a RFL treated nylon knit fabric) and the moisture-impervious coating (such as rubber) would be on the bondside surface of the second fabric ply. The coating on the breezeside of the first fabric ply and/or the coating on the bondside of the second fabric ply may be texturized. Additionally or alternatively, the bondside surface of the first fabric ply may also be coated with a moisture-impervious coating and/or the breezeside surface of the second fabric ply may also be coated with a moisture-impervious coating.
These and other features of the invention are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative of but one of the various ways in which the principles of the invention may be employed.